Advanced materials and technologies for modern constructions
Currently VNIINM is one of the leaders in Russia and globally in the field of application of protective and functional coatings of a wide range of application with a variety of processes that allow producing new-generation products with radical improvement in the price/quality ratio.
With the advanced innovations of VNIINM that have no domestic counterparts, a modern industrial production of functional nanostructured coatings using a wide range of materials, technologies and equipment for their application is established. The created technology-based system will become one of the basic elements to restore the domestic machine-building sector, improve the efficiency, reliability, and enhance the operational capabilities of engineering products for fuel and energy, petrochemical and mining, energy and aviation turbine construction and other industries.
According to the CEO of VNIINM Valentin Ivanov, they have developed over a dozen surface treatment technologies for the conversion applications, such as high-speed ion plasma magnetron sputtering, cathode spraying and flame treatment in an inert atmosphere. In addition, VNIINM uses non-vacuum methods, e.g. cold spray, electrospark doping, microarc oxidation, chemical and thermal treatment in special environments, abrasive blast treatment, magneto-abrasive treatment and ColdJet treatment. Depending on the surface and task, ceramic, metal, composite and other materials can be applied.
The expert in materials and designers of the Institute are trying to solve problems facing the industry and national economy that concern applying protective and functional coatings by choosing the most effective, practically feasible and cost-effective methods.
An effective method of application functional and wear-resistant coatings on new products, as well as the restoration of worn parts is cold spray or supersonic air-and-powder spraying based on the effect of fixing solid particles that move with supersonic speed and have a high kinetic energy at high velocity impact on the product surface.
Cold spray technologies developed in VNIINM use metal powders (aluminium, copper, zinc, nickel, lead, tin, babbit, iron, cobalt, vanadium and titanium), alloys or their mechanical mixtures with ceramic powders. They allow to apply metallic and ceramic coatings not only on metals but also on glass, ceramics, stone, concrete and even dense organic materials, i.e. carbon fibres, vacuum rubber and plastics.
As a result of treatment, the surface acquires the desired characteristics, heat resistance, mechanical durability, antifriction properties, corrosion resistance, radar absorption and electrical insulation. The coatings are a uniform layer of densely packed and deformed metal particles with embedded ceramic particles.
Fig. 1 and 2 show a semi-automated and robotic (automated) cold spray coater. By changing the mode of operation of the equipment, the product surface automatically undergoes either the erosional treatment or coating of the desired composition, porosity and thickness.
In some cases, to improve the corrosion resistance, heat resistance and wear resistance of coating it is necessary to create a diffusion (intermetallic) layer through heat treatment, the modes of which are chosen experimentally. In some cases, after spraying and heat treatment, coating is ground to a desired level of roughness.
The cold spray method is well-known and common but it is quite a challenging technical objective to develop technologies to place coating on specific parts and products.
VNIINM has successfully developed coating process diagrams depending on the type of products, and some of the methods are patented.
As part of functional coating with the cold spray method, VNIINM has entered into 18 agreements on cooperation in aviation, medical, drilling equipment, shipbuilding, housing maintenance and utilities services, railway transport, electrical engineering and electronics (termination pads, high-temperature superconductivity) and construction.
for housing and communal services
One of the VNIINM conversion projects was designed to cooperate with the prefecture of the North-West Administrative District of Moscow aimed at introducing new technologies in the housing maintenance and utilities sector. In the summer of 2014 some tests were successfully carried out with regard to metal coating for rapid repair and restoration of water supply systems; and the project was extended with a practical effect. VNIINM experts demonstrated the feasibility of the cold spray method to refill the pipe damages. Damage was repaired without blocking any lines while the repaired section can successfully withstand pressure differentials.
Corrosion damage is one of the mass operation-related damages of the ‘aging’ aircraft, so it is the right time to develop a technology allowing to efficiently and effectively carry out repairs and restoration of airframe components by companies that operate the aviation equipment.
In cooperation with the State Research Institute of Civil Aviation (GosNIIGA) VNIINM has been working on an experimental evaluation of the effectiveness of structural restoration of the corroded aluminium alloys to maintain the airworthiness of an aircraft. At the initial stage, VNIINM experts conduct a preliminary assessment of the impact from the composition of the powder mixture and the chosen material recovery technology on the statistical strength and elasticity by specimens tensile testing under static loading. The structural duralumin (based on AL-Cu-Mg) used in the modern aircraft design was chosen as the test object.
To restore the structural elements by VNIINM researchers, the supersonic air-powder material coating technology that can ‘heal’ surface defects in conjunction with mechanical treatment (abrasion and polishing) was developed and applied. The process includes preparing the surface of the product to spraying; repair of damage by supersonic spraying the powder composition on corresponding sections; levelling the surface; additional surface treatment; finishing supersonic air-powder coating with powder compositions.
All of these works can be carried out manually on the site of the client operating the aviation equipment. In addition, the mobile cold spray system developed by VNIINM with a weight of less than 25 kg will allow repair damage in the field.
These results obtained show that corrosion damage can be effectively ‘healed’ and given the right composition of the powder composition and its right deposition, coating in the repaired area is not destroyed until the yield point or higher is reached; and its elastic and plastic properties maximally correspond to the properties of the base material.
A wide range of challenges faced by engineers and designers in the field of functional and protective coatings require new approaches. High-speed ion plasma magnetron sputtering is an effective method of modifying the surface. In this case, the material to be applied to the surface of parts or products is placed at the cathode of a special device and is sprayed in the argon atmosphere at a residual pressure of 1…10-1 Pa. Under the influence of bombardment with argon ions, a flow of atoms is generated from the cathode which is carried on the surface of the product and is deposited to form the coating. The coating process is carried out on special vacuum units. It is a multiple-purpose method allowing to obtain nanostructured coatings from various materials such as metals, alloys, composites, ceramics and chemical compounds, wherein the coating composition is determined by the composition of the initial target for sputtering. The deposition rate in the high-speed mode with the distance between the target and part of 50-60 mm for various materials is between 20 and 150 microns/hour.
With this method you can effectively and efficiently address the following scientific and technology-related objectives:
•improve the heat resistance of the turbine blades of gas turbine engines (GTE) the fifth-generation for aircraft and ships by the use of multi-layer and multi-component coatings based on aluminide and aluminozirconium wholistically alloyed with elements that, on the one hand, stabilise the formation of protective oxides, on the other hand, the heat resistance of the material base and coating;
•increase in the service life of the GTE compressor components, fuel injection equipment of hydraulic systems, wing wings, turbojet engines for aircraft and rocket vehicles through the use of composite coatings including those that are wear-resistant, solid lubricating and corrosion-resistant with the ultrafine structure;
•increase in the service life, heat resistance of the valve-piston pair of the internal combustion engine (ICE), ICE diesel fuel equipment and other elements of the vehicle through the use of multi-layer and multi-component coatings based on high-temperature alloys with high corrosion and reflective properties;
•apply the solid lubricant coating, antiprehensive coating on gears of the heavily loaded gears to reduce energy consumption, improve reliability and reduce noise;
•apply coatings on high-speed rolling bearings, threaded joints of drill pipes, threaded joints of quick-detachable systems etc.;
•partially replace the environmentally harmful chemical-and-electrochemical technologies used for corrosion protection and creation of decorative properties for the motor vehicle products through the use of multi-component coatings based on stainless steel, "aluminium-chromium" alloys and others with high corrosion-resistance and light-reflecting properties.
It should be noted that the accomplishment of each specific task of coating on a product or item requires an individual material spraying approach, method or technology. For best results, the VNIINM scientists together with designers and developers combine different methods of modifying the surface of a product.